Home Heating Help

Yankee,
Your end of loop heating problem is probably caused by your system’s inability to maintain adequate static pressure to raise the water in the piping to the last radiators. If that’s the case, that problem alone can be solved by adding, replacing or simply adjusting a pressure regulating fill valve at the boiler.
That said, here are your answers:

a. Yes. Depending on how your system is piped, creating two heating zones from one is done by one of the following methods:
1. Piping new connections to one of the proposed zone’s radiators and back to the boiler with its own pump, leaving the other radiators as they are.
2. Adding individual flow-regulating valves, sometimes called TRVs, to each radiator or to the radiators serving the overheated spaces.
3. Redesigning and repiping the entire system to properly address the individual energy demand of each heated area.
There are sometimes other band-aid type methods but those are best left explored on a by-case basis.

b. Nothing will solve your particular problem if there is no provision made to maintain adequate system pressure.

c. According to your post, you’ve got a true tankless coil water heater. These days “tankless” has taken on a different meaning. The new tankless is good, what you have is not-so-much good. Your boiler burns at its maximum capacity to maintain temperature within itself to keep hot water on the ready without actually storing any appreciable amount of it. That means a coil of copper tubing sits in your boiler’s water and absorbs the heat surrounding it as you draw water through it by opening a faucet. It does this at a very high rate of fuel use; about 50,000 BTUs per gallon of water used. So when you take a shower at 3 gallons per minute, your boiler runs for….um…. a long time… to make up that energy spent. My advice is to change this setup, to just about anything else, when you are ready to change the boiler.

d. Just about anything you do to create smaller zones and update your current system will, if well designed and executed, reduce heating costs and increase comfort.

Too wordy?

Posted by: Master Plvmber at July 29, 2008 12:51 PM

I prefer gas to oil for any number of reasons, but I've recently gotten some hate mail from some oil guys that I won't take lightly. In the end we agree that both fuels have their audience and the consumer should do his or her own research and decide what's right for them.

That aside, I feel like a boiler is a twenty-year investment and oil as a heating fuel is becoming less common every year.

You really need to ask your fellow end-users their opinions.

If you're installing a new boiler, have the plumber put a price on his way of creating a two-zone system for you while he's working in the house anyway. That way you can expect to avoid some travel and set up costs. I'd go for the indirect water heater. When I install them, I never hear about them again. No one notices a difference in their hot water delivery and the bills go down. Tankless water heaters can drive some people crazy. Others are just ecstatic with them. It depends much upon the lifestyle of the residents.

As for the pressure question: it takes one pound of pressure to lift water 2.31 feet, or about 27 inches.
The correct amount of pressure in a hot water heating system is the height from the base of the boiler to the top of the highest radiator divided by 2.31 plus an additional 4-5 psi.
Your plumber might not know that. I'd have him check.

Posted by: Master Plvmber at July 29, 2008 4:09 PM

If your boiler is fitted with an 8gpm coil, you must have a boiler that burns 400,000 btus per hour.
If your tenants are using 3gpm showerheads it is assumed they are passing 75% hot water and 25% cold water to mix to a comfortable temperature.
3 simultaneous users will pull 6.75 gpm (75% of 9 gpm) through the coil. The water running through that coil will extract about 338,000 BTUs from the boiler water, but your boiler will be adding 400,000 BTUs (minus about 20% for an 80% efficient boiler) at the same time. So you're close without having any storage.

All that energy is stored then spent then replenished by the boiler water and burner, and the output can't exceed the ratings of the coil or the input of the burner so I seriously doubt it costs any more or less to run showers one after the other or simultaneously.

The real alternative for you is to install a hot water holding tank of some kind and let the boiler rest between uses and run longer cycles, which is more efficient, on a call to reheat the tank. That way, the boiler need not fire as many times per hour as it does to maintain 160 degrees or so of boiler water when it may not be used all day.
Honestly, La di da di, yours is a light commercial application that requires more thought and figuring than should be done here. If you were serious about some options, you should get someone to do a site visit and see and show you exactly what would make most sense.

Posted by: Master Plvmber at July 29, 2008 4:32 PM

5:55. With all due respect, I have no idea how you came to that conclusion by what I said. I'm not saying that at all.

6:02. You're way oversimplifying it by assuming for how long the boiler will run. It is not a direct ratio to how long someone is in the shower or even gallons per minute or BTUs used.

Posted by: Master Plvmber at July 29, 2008 6:40 PM

You're welcome.

FLH,
There's no good reason not to insulate any water or steam-carrying pipe.
Cold water pipes build up condensation in the presence of warmer surrounding air and humidity.
Bare 3/4" copper hot water pipe looses 30 BTUs per foot.
Bare 2" steel steam pipe looses 240 BTUs per foot.
The way to stop that is to insulate them.

The Code says to use 1" thick insulation, it doesn't say to use foam, fiberglass or any other material specifically. Fiberglass tubes are best for steam and hot water.
Don't get crazy about wrapping the joints, but, when talking about insulating heating pipes, more actually is more.

Posted by: Master Plvmber at July 29, 2008 10:09 PM